btrfs: split discard handling out of btrfs_map_block

Mapping block for discard doesn't really share any code with the regular
block mapping case.  Split it out into an entirely separate helper
that just returns an array of btrfs_discard_stripe structures and the
number of stripes.

This removes the need for the length field in the btrfs_io_context
structure, so remove tht.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 27 insertions, 40 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 7513e45c0c42..12a6150ee19d 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -5913,18 +5913,17 @@ void btrfs_put_bioc(struct btrfs_io_context *bioc)
 		kfree(bioc);
 }
 
-/* can REQ_OP_DISCARD be sent with other REQ like REQ_OP_WRITE? */
 /*
  * Please note that, discard won't be sent to target device of device
  * replace.
  */
-static int __btrfs_map_block_for_discard(struct btrfs_fs_info *fs_info,
-					 u64 logical, u64 *length_ret,
-					 struct btrfs_io_context **bioc_ret)
+struct btrfs_discard_stripe *btrfs_map_discard(struct btrfs_fs_info *fs_info,
+					       u64 logical, u64 *length_ret,
+					       u32 *num_stripes)
 {
 	struct extent_map *em;
 	struct map_lookup *map;
-	struct btrfs_io_context *bioc;
+	struct btrfs_discard_stripe *stripes;
 	u64 length = *length_ret;
 	u64 offset;
 	u64 stripe_nr;
@@ -5933,29 +5932,26 @@ static int __btrfs_map_block_for_discard(struct btrfs_fs_info *fs_info,
 	u64 stripe_cnt;
 	u64 stripe_len;
 	u64 stripe_offset;
-	u64 num_stripes;
 	u32 stripe_index;
 	u32 factor = 0;
 	u32 sub_stripes = 0;
 	u64 stripes_per_dev = 0;
 	u32 remaining_stripes = 0;
 	u32 last_stripe = 0;
-	int ret = 0;
+	int ret;
 	int i;
 
-	/* Discard always returns a bioc. */
-	ASSERT(bioc_ret);
-
 	em = btrfs_get_chunk_map(fs_info, logical, length);
 	if (IS_ERR(em))
-		return PTR_ERR(em);
+		return ERR_CAST(em);
 
 	map = em->map_lookup;
+
 	/* we don't discard raid56 yet */
 	if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
 		ret = -EOPNOTSUPP;
-		goto out;
-	}
+		goto out_free_map;
+}
 
 	offset = logical - em->start;
 	length = min_t(u64, em->start + em->len - logical, length);
@@ -5981,7 +5977,7 @@ static int __btrfs_map_block_for_discard(struct btrfs_fs_info *fs_info,
 	 * device we have to walk to find the data, and stripe_index is
 	 * the number of our device in the stripe array
 	 */
-	num_stripes = 1;
+	*num_stripes = 1;
 	stripe_index = 0;
 	if (map->type & (BTRFS_BLOCK_GROUP_RAID0 |
 			 BTRFS_BLOCK_GROUP_RAID10)) {
@@ -5991,7 +5987,7 @@ static int __btrfs_map_block_for_discard(struct btrfs_fs_info *fs_info,
 			sub_stripes = map->sub_stripes;
 
 		factor = map->num_stripes / sub_stripes;
-		num_stripes = min_t(u64, map->num_stripes,
+		*num_stripes = min_t(u64, map->num_stripes,
 				    sub_stripes * stripe_cnt);
 		stripe_nr = div_u64_rem(stripe_nr, factor, &stripe_index);
 		stripe_index *= sub_stripes;
@@ -6001,31 +5997,30 @@ static int __btrfs_map_block_for_discard(struct btrfs_fs_info *fs_info,
 		last_stripe *= sub_stripes;
 	} else if (map->type & (BTRFS_BLOCK_GROUP_RAID1_MASK |
 				BTRFS_BLOCK_GROUP_DUP)) {
-		num_stripes = map->num_stripes;
+		*num_stripes = map->num_stripes;
 	} else {
 		stripe_nr = div_u64_rem(stripe_nr, map->num_stripes,
 					&stripe_index);
 	}
 
-	bioc = alloc_btrfs_io_context(fs_info, num_stripes, 0);
-	if (!bioc) {
+	stripes = kcalloc(*num_stripes, sizeof(*stripes), GFP_NOFS);
+	if (!stripes) {
 		ret = -ENOMEM;
-		goto out;
+		goto out_free_map;
 	}
 
-	for (i = 0; i < num_stripes; i++) {
-		bioc->stripes[i].physical =
+	for (i = 0; i < *num_stripes; i++) {
+		stripes[i].physical =
 			map->stripes[stripe_index].physical +
 			stripe_offset + stripe_nr * map->stripe_len;
-		bioc->stripes[i].dev = map->stripes[stripe_index].dev;
+		stripes[i].dev = map->stripes[stripe_index].dev;
 
 		if (map->type & (BTRFS_BLOCK_GROUP_RAID0 |
 				 BTRFS_BLOCK_GROUP_RAID10)) {
-			bioc->stripes[i].length = stripes_per_dev *
-				map->stripe_len;
+			stripes[i].length = stripes_per_dev * map->stripe_len;
 
 			if (i / sub_stripes < remaining_stripes)
-				bioc->stripes[i].length += map->stripe_len;
+				stripes[i].length += map->stripe_len;
 
 			/*
 			 * Special for the first stripe and
@@ -6036,17 +6031,17 @@ static int __btrfs_map_block_for_discard(struct btrfs_fs_info *fs_info,
 			 *    off     end_off
 			 */
 			if (i < sub_stripes)
-				bioc->stripes[i].length -= stripe_offset;
+				stripes[i].length -= stripe_offset;
 
 			if (stripe_index >= last_stripe &&
 			    stripe_index <= (last_stripe +
 					     sub_stripes - 1))
-				bioc->stripes[i].length -= stripe_end_offset;
+				stripes[i].length -= stripe_end_offset;
 
 			if (i == sub_stripes - 1)
 				stripe_offset = 0;
 		} else {
-			bioc->stripes[i].length = length;
+			stripes[i].length = length;
 		}
 
 		stripe_index++;
@@ -6056,12 +6051,11 @@ static int __btrfs_map_block_for_discard(struct btrfs_fs_info *fs_info,
 		}
 	}
 
-	*bioc_ret = bioc;
-	bioc->map_type = map->type;
-	bioc->num_stripes = num_stripes;
-out:
 	free_extent_map(em);
-	return ret;
+	return stripes;
+out_free_map:
+	free_extent_map(em);
+	return ERR_PTR(ret);
 }
 
 /*
@@ -6204,7 +6198,6 @@ static void handle_ops_on_dev_replace(enum btrfs_map_op op,
 					bioc->stripes + i;
 
 				new->physical = old->physical;
-				new->length = old->length;
 				new->dev = dev_replace->tgtdev;
 				bioc->tgtdev_map[i] = index_where_to_add;
 				index_where_to_add++;
@@ -6245,8 +6238,6 @@ static void handle_ops_on_dev_replace(enum btrfs_map_op op,
 				bioc->stripes + num_stripes;
 
 			tgtdev_stripe->physical = physical_of_found;
-			tgtdev_stripe->length =
-				bioc->stripes[index_srcdev].length;
 			tgtdev_stripe->dev = dev_replace->tgtdev;
 			bioc->tgtdev_map[index_srcdev] = num_stripes;
 
@@ -6600,10 +6591,6 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
 		      u64 logical, u64 *length,
 		      struct btrfs_io_context **bioc_ret, int mirror_num)
 {
-	if (op == BTRFS_MAP_DISCARD)
-		return __btrfs_map_block_for_discard(fs_info, logical,
-						     length, bioc_ret);
-
 	return __btrfs_map_block(fs_info, op, logical, length, bioc_ret,
 				 mirror_num, 0);
 }